This invention relates to the art of electrical circuit component manufacture and, more particularly, to improved means, including both the article and method, for anchoring terminal leads or pins to a substrate and a circuit component supported by the substrate.
The increasing need for miniaturization of electrical components and the forming of electronic packages therefor has dictated the requirement for suitable substrates or bases upon which the components and circuits may be disposed. Obviously, care is required in the selection of terminals and leads for mechanically interconnecting the components and the circuits. Very often, the insulating substrates for supporting the circuits are of relatively fragile or frangible materials such as alumina or other ceramic materials. This is particularly true in the case of components utilizing electrical circuitry of the so-called "cermet" or thick film or even thin metallic or carbonaceous film materials disposed upon a substrate capable of being fired to join the film with the substrate. Obviously, it is advantageous to utilize a minimal thickness of substrate, which also tends to add to the weakness of construction.
Typically, terminal leads have been attached to a substrate to provide an electrical connection to a circuit layer, such as a resistor or other conductive film deposited on the substrate, by means of soldering, mechanical crimping or by force fitting the leads into cavities formed in the substrate.
The field of the present invention is directed to the attachment of leads to a substrate bearing a conductive circuit and, particularly, to those terminal leads having a portion thereof protruding through an aperture in the substrate and adapted to be swaged or otherwise upset by applying a force directly to the end of the portion of the lead member. This force forms a laterally extending flange-like portion for clamping engagement with the lead surface positioned on opposite sides of the apertured substrate. Examples of prior art devices utilizing swaging or upsetting methods of attaching leads may be found in U.S. Pat. Nos. 2,717,943 granted to Daily et al. on Sept. 13, 1955; 3,257,708 granted to Stricker on June 28, 1966; 3,537,056 granted to Van Benthuysen et al. on Oct. 27, 1970 and 3,659,245 granted to Payne on Apr. 25, 1972. British Pat. No. 737,998, published Oct. 5, 1955 and invented by E. J. Madle, also shows means of joining leads to substrates.
In general, although attachment techniques utilizing swaging or upsetting procedures have contributed to an inexpensive and facile method of manufacturing miniaturized devices, these same techniques have also required close control, specific attention to alignment of tooling and close attention to manufacturing tolerances of the mating parts. This degree of control obviously has led to a relatively high "scrap rate". In the case of devices such as the resistance units of potentiometers and circuit trimming devices, as well as network substrates, the resistive elements will have previously gone through several stages of manufacture prior to attachment of termination leads. Should the devices at this stage become damaged, it will be apparent that their inherent value will be relatively high and that it is even more important to minimize scrap at this point of manufacture. When devices are miniaturized, it will be obvious that the size of the substrate must be kept to a minimum -- a requirement that limits the stress-bearing cross section of the substrate. Successful swaging or upsetting operations therefore require that the component parts be specifically designed for stress-bearing efficiency.